This section provides background information to facilitate a better understanding of the various aspects of the invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
The invention relates generally to temperature measuring techniques, and, more specifically, to devices and methods for optical measurement of temperature in an environment.
Optical temperature measuring techniques are well known in the art. There are several optical phenomena which can be exploited to enable temperature measurement by a sensor, analogous to the way in which thermocouples exploit the thermoelectric effect. These optical methods include white light interferometry, photonic band-gap measurement, and photoluminescent decay. Each method has advantages and disadvantages which limits their general application.
Photoluminescent temperature measurement techniques are particularly suitable for applications in environments having strong electric and/or magnetic fields and the like, where metal sensors cannot be relied upon to provide accurate results because the metal is heated when immersed in the electromagnetic field, causing a bias in the readings. In addition, sensors utilizing metal components and conductors often provide an unsafe path for dielectric breakdown in environments where high voltages are present.
Photoluminescent decay methods comprise the use of a material with photoluminescent properties which are temperature dependent. Typically in the form of a sensor at the end of a fiber optic cable, the photoluminescent material is excited to luminescence by sending excitation radiation of one wavelength to the sensor, and the resulting light emitted through photoluminescence (the photoluminescent light) at a different wavelength is photo-detected. The detected signal is then processed to determine the temperature of the photoluminescent material in the sensor. The prior art photoluminescent temperature sensing devices and methods utilize separate optical devices for the source of the incident light and for the photodetector.